Patients inclusion : adult severe TBI (glasgow coma score < 9) < 66 yrs Exclusion criteria : polytrauma, bilateral fixed dilated pupils, motor score < 4, neurosurgery, prolonged episode of hypoxia or arterial hypotension, 34 patients included from november 2003 to november 2004 and randomized into two groups : MAN group receiving mannitol 20% 100 ml in 15 min (17 patients, 36 episodes of IHE treated) and LAC group receiving semimolar sodium-lactate 100 ml in 15 min (17 patients, 37 episodes of IHE treated). For ethical reasons a rescue treatment in a crossover fashion was performed for each episode of IHE when the randomized treatment failed.